Molded core



July 5, 1949. c. A. HORN 2,475,321

MOLDED CORE Filed June '22, 1943 IINV ENTOR. Clarence A H0571! 79 A .vfi 6J Aftys.

Patented July '5, 1949 MOLDED CORE Clarence A. Horn, West Orange, N. 3.,asslgnorto Henry L. Crowley, South Orange, N. J.

Application June 22, 1943, Serial No. 491,765

3 Claims. 1

This invention relates to improved machinery and methods by means ofwhich improvements in molded metal products may be secured.

The subject matter of this invention is concerned with metal bodiesmolded from metal powders and particularly with iron cores molded frompowdered iron and constructed for use as a core for current carryingcoils of electrical apparatus of various types. For example in someforms of radio circuits it is a practice at the present time to providethe tuning coils thereof with iron cores which may be longitudinallyadjusted with respect to the coils to vary the inductance thereof. Inorder to facilitate such adjustments these cores are provided with athreaded rod or screw at one end which is secured in place by beingmolded therein during the formation of the core. The threaded rodextends beyond the end of the core a suitable distance and in use passesthrough a plate or other support in threaded engagement so that uponrotation the core is caused to move longitudinally.

Cores of this type are molded from extremely fine iron powders undervery high pressures in a ram type of press having a fixed die forming apocket into the opposite ends of which the rams move to compactthepowder under such high pressure as to cause the particles to becomepermanently bonded together. The durability of such core is commonlyincreased by sintering the molded product after compression.

vOne of the movable rams is provided with a central bore in which thethreaded rod for the core is mounted with the end projecting so as to beinserted into the powder during molding. The rams, of course, have asliding fit in the fixed die, but there is suflicient clearance so thatunder the extremely high pressures encountered some of the powderedmetal will flow around the periphery of the ram a short distance intothe space between it and the adjacent wall of the fixed die. Likewisesome of the powder will flow under pressure into the space around thethreaded rod between it and the surrounding wall forming the recess inthe ram in which the screw is mounted. As the result of this escape ofpowdered metal there are formed fins which are termed in the art flashesat the ends of the core around the outer peripheral edges and around theprojecting screw. The outer peripheral fins are easily removed, but itis a more difficult and less satisfactory operation, as well as anexpensive one, to remove the flash around the screw which, of course, ismolded into the threads of the screw.

If the material of the flash around the screw is not completely removedit will ultimately work loose when the core is in use, producing a fineiron powder or dust which gets through the electrical equipment andbecomes a nuisance even if it does not, as it often may, disturb theelectrical characteristics of the equipment. For example, in the case ofultra high frequency radio circuits a small amount of iron powder loosein the coils may cause electrical disturbances of undesirable magnitude.

The subject matter of this invention is concerned with a method ofmolding metal cores and projecting screws so as to overcome thediihculty particularly encountered with the flash which forms about thescrew.

This invention resides substantially in the combination, construction,arrangement, relative location of parts, steps, series of steps, and theproduct, all as hereinafter described in full detail.

In the accompanying drawing,

Figure 1 is a vertical, central, cross-sectional view through a metalpowder molding press showing the manner of molding the screw in a moldedbody and the flash forms;

Figure 2 is a similar view of such a press modifled in accordance withthis invention;

Figure 3 is a vertical, central, cross-sectional view of one end of acore manufactured in accordance with this invention; and

Figure 4 is a top plan view thereof. In the usual metal outer moldingprocess a press capable of producing very high pressures.

per square inch, say of the order of 100,000 pounds per square inch isprovided. It includes a fixed die l0 which is a-body of steel having apassage therethrough of the configuration of the body to be molded. Thecore illustrated is of circular cross-section, and hence the passagethrough the fixed die lllis circular in cross-section. The lower end ofthe passage is closed by a bottom ram ll. With the ram H in lowermostposition closing the bottom end of the opening, a predetermined quantityof metal powder is poured into the chamber thus formed. The top ram I2is provided with a recess IS in which the screw It to be molded into thecore is inserted. As the rams are moved towards each other the metalpowder is compressed into a coherent body It: in which the screw it isembedded. Due to the enormous pressures employed some of the powder willflow into the space between the ram l2 and the die in to form a flash orfln, as indicated at [6. In a like manner a flash I! will form aroundthe screw. Of course, a flash will form 7 3 at the bottom of the core [5around the bottom ram, although this has not been illustrated in thedrawings. The rams arewithdrawn, freeing the molded body. The flash i9is easily broken oil, but the flash it is harder to eliminate. Thedescription of the above old practice will be helpinvention.

This subject matter is illustrated in Figures 2, 3 and 4. The fixed diel and bottom ram ii are the same as the arrangement of Figure 1. The topram i2 is however provided with a projecting collar I8 surrounding therecess l3 and of a length beyond the end of the ram at least equal tothe normal length of the flash H which forms. When the body i5 is formedby compression the flash it will form as well as one at the bottom endand the flash i'i will also form around the screw M. However, asillustrated in Figure 3, the recess M in the end of the core or body i5is of such longitudinal length that the flash B? which forms will bewithin the end of the core, and hence out of the region of that portionof the screw I 4 which must cooperate with a threaded support. Thus itis not necessary to o to the expense or bother of removing the flash i7and it is so positioned and projected that it will not normally bebroken loose during the use of the device. Of course, the flash formedaround the outer periphery at the ends of the core is easily removed,and therefore no' provision is made in accordance with this inventionfor special handling thereof as in the case of the flash ET.

From the above description it will be apparent to those skilled in theart that the subject matter of this invention is capable of somevariation, and I do not, therefore, desire to be strictly limited to thedisclosure as given for illustrative purposes, but rather by the scopeof the claims granted me.

What is claimed is:

1. A molded body composed of densely compacted particles of metal havinga screw embedded therein and projecting beyond one face 4m inunderstanding the subject matter of this 4 thereof, said body having arecess surrounding said screw of an axial len th at least equal to thematerial of the body which flashes around the screw.

2. A magnetizable core comprising a formsustaining body of ironparticles with a metal insert embedded therein and projecting beyond oneface thereof, said body having a recess opening at said iaceand' lyingconcentric with said metal insert whereby the material which flashesaround the insert will lie in the recess.

' 3. A method of molding a body of powdered metal with an insertembedded therein and projecting from one face, which comprisescompacting the metal powder into a shape to form a recess in theresultant body surrounding the insert and simultaneously forming a flashat the periphery of said face and in the recess in said face surroundingthe insert, and fixing said insert extending through said recess andbeyond said face, said recess having an axial length at least equal tothe height of the flash surrounding the insert.

CLARENCE A. HORN.

REFERENCES (Ci'lilED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Great Britain Oct. 7, 1935-

